So, here is what's going on... I have a 94 4runner with a 4" IFS lift with 33x12.50 tires..
I'm driving on the freeway this morning at about 70mph, and when I take my foot off the gas and coast I can hear a grinding noise from the rear/middle of the truck... but then when I gas it again then the noise goes away.

any ideas? it could be my driveline, but who knows

Is your transfer case a slip yoke or fixed yoke? You may need a SYE (slip yoke eliminator). It sounds just like the same thing I had when I lifted my truck. How recently did you lift it?

This sounds like the same noise my truck makes. I don't know what it is either. Like yours, it comes on when I let off the gas. Anyone know? I thought it might be a bearing.........

Toyotas don't use slip yokes.

Check your U-joints to make sure they're not worn. Good idea to lube them while you're under there. Check your transmission and transfer case oil levels.

It's definately your driveline :D But there's many different parts it could be.

Auto or standard?

Next time you make a post, put the vehicle in the subject, you'll get more responses.

damn... I get the same noise. Someone said it was the slip yoke, but I don't see why.

I don't have an SYE.

I have about 3 1/2" of lift on it.

Check your U-joints. That is what was wrong with mine. It took me forever to figure it out, but save yourself some embarrasment and a lot of trouble and start by checking them. Whatever you do don't send it to a damn shop just to find out it's the u-joints. That'll make you feel really stupid.:flipoff2: :D

I'd say U-joints too, i had the same problem in my old truck and i felt stupid when i found out it was just a u joint.